Use of urea and n-methylol compounds in mineral dyeing of fabric

ABSTRACT

A practical mineral dyeing process for imparting to cellulosic textiles the qualities of improved dimensional stability, resistance to actinic degradation, and resistance to microbial degradation is produced. The textiles are simultaneously mineral dyed and treated with N-methylol resin and urea mixtures to minimize the tendering of the textiles which is generally associated with the use of metal chlorides upon overdrying.

United Staes Patent [72] Inventors Carl ll-llamalainen Metairie;

Hubert 1-1. St. Mard, New Orleans; Albert S. Cooper, Jr Metalrle; Wilson A. Reeves, Metalrte, all 011 La.

June 24, 1970 Nov. 23, 1971 The United States at America as represented by the Secretary of Agriculture Appl. No. Filed Patented Assignee USE OF UREA AND N-METHYLOL COMPOUNDS IN MINERAL DYEING OF FABRIC 56] References Cited FOREIGN PATENTS 574,814 1/1946 Great Britain 8/52 730,601 5/1955 Great Britain 8/52 OTHER REFERENCES Horday, Journal of the Society of Dyers and Colourists, pp. 87- 90, April, 1945.

American Dyestuff Reporter, pp. 705- 710, Dec. 1, 1947. Primary Examiner Donald Levy Assistant Examiner-J. Cannon AllorneysR. Hoffman and W. Bier USE OF UREA AND N-METHYLOL COMPOUNDS IN MTNERAL DYEING F FABRIC A nonexclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to a mineral dyeing process for imparting to cellulosic materials dimensional stability and resistance to actinic and biological degradation.

Specifically, this invention relates to a process for imparting to cellulosic materials resistance to degradation by deposition of metal oxide with concurrent deposition of N-methylol resin.

More specifically, this invention relates to a process of mineral dyeing with chromic chloride, iron chloride, and the like in which the addition of urea and N-methylol resins reduces the amount of strength loss due to treatment and results in improved dimensional stability and resistance to actinic and biological degradation, and weathering in general.

The cellulosic textiles treated by the process of this invention find use in the fabrication of awnings, boat covers, canvas tops, tarps, shade umbrellas, shoe liners, irrigation liners, agricultural shade cloth, and covers, and the like. All areas of fabric use which presently may be inhibited by outdoor or indoor bacterial, fungal, and/or actinic degradation will find application of this process beneficial.

The prior art teaches the application of chrome oxide and/or iron oxide mineral dyeings in the pad with chromic chloride and/or iron chloride solution, dry to about 7 to 8 percent moisture, pad with caustic-soda ash, then wash with soap, rinse, and dry. A critical part of the process is the first drying step. Overdrying tenders the fabric and underdrying causes the heavy metal hydroxide or heavy metal oxide to form outside the fibers and to contaminate the caustic-soda ash after causing excessive wear of roll bearings from the accumulation of the abrasive metal oxide particles in the bath. The cause of the tendering is the free acid in the chromic chloride and/or iron chloride bath.

The main object of this invention is to bufier the tendering effect of the chromic chloride and/or iron chloride on overdrying through the use of organic nitrogen compounds such as urea, thus minimizing a critical problem in the process. Thus, when fabric is padded with chromic chloride and/or iron chloride solutions containing buffers, complete drying is accomplished without the fear of the degradation previously due to overdrying.

The second object of this invention is to confer rot and weather resistance to cellulosic fabric by the application of certain N-methylol finishing agents. These nitrogeneous agents also result in some buffering of the chromic chloride and/or iron chloride tendering but not quite to the same extent as does urea. Rot resistance is not inherent in fabrics treated with chromic chloride and/or iron chloride alone or with chromic chloride and/or iron chloride with urea added.

A third object of this invention is to produce a mineral dyed fabric with improved dimensional stability and resistant to actinic and biological degradation by incorporation of urea and N-methylol resins in the chromic chloride and/or iron chloride treating solutions. The use of chromic chloride results in a green-gray shade of color which has been accepted industrially and is known in the trade as pearl-gray." Variations in color to various shades of khaki can be accomplished by substituting part of the chromic chloride with iron salts such as iron chloride.

In general our present invention can best be described as a process for imparting to cellulosic materials a pearl-gray" colored mineral dyeing having improved dimensional stability, resistance to actinic degradation, and resistance to microbiological degradation wherein the combined properties are obtained on the finished product by combining mineral dyeing with N-methylol resins in one application comprising:

a. impregnating a cellulosic material with a mixture containing about percent chromic chloride, 6 percent to percent of an N-methylol resin such as a trimethylolmelamine or ureaformaldehyde, 5 percent to 10 percent urea, and 0.2 percent of a wetting agent,

b. removing the excess mixture of solutions from the impregnated cellulosic material to obtain about 40 percent to 70 percent wet pickup,

c. drying the wet impregnated cellulosic material for about 3 to 5 minutes at a temperature selected to insure thorough drying (i.e., 282 F and polymerization of the N-methylol resin,

d. treating the dried fabric from c. above by padding with hot F.) solution of caustic and soda ash containing about 1.6 percent sodium hydroxide and 2.8 percent sodium carbonate, and

e. washing the resulting fabric free of alkali and then drying The embodiment of this invention is demonstrated more specifically in the following examples.

EXAMPLE I TABLE I Effect of Drying Time on Strip Breaking Strength of Mineral Dyed Cotton Duck Fabric Drying Time Strip Break Strength Minutes pounds 0.5 144 I .0 144 1.5 142 2.0 133 3.0 99 4.0 99 5.0 88 control I34 EXAMPLE 2 Various amounts of urea were added to the chromic chloric treating solutions. The 8 oz. lined duck fabric was padded with the solutions, dried 5 minutes in a gas fired oven at 282 F treated with hot (160 F.) caustic-soda ash solution, then washed and dried. The effect of the urea on the breaking strength and solution pH is shown in the accompanying table.

TABLE lI Effect of Urea on Solution pH and Strip Breaking Strength of Mineral Dyed Cotton Duck Fabric Solution pl-l appeared to be only slightly afiected with increasing urea concentration. The buffering effect of urea on the degradative effect of chromic chloride acidity on heating is clearly shown. As little as 10 percent urea results in better than 90 percent strength retention.

EXAMPLE 3 In mineral dyeing, chromic chloride is frequently used in combination with ferric salts to obtain some variety of color. Chromic chloride by itself produces a pearl-gray color; ferric chloride results in an orange-yellow color; and various shades of tan or khaki result from mixtures of the two. Lined 8 oz. duck fabric was treated with solutions of these individual salts and with mixtures of solutions of these salts both with the without added urea. After padding, the fabrics were dried 5 minutes at 282 F drying was followed by treatment with hot alkali, then the fabrics were washed and dried. The following table lists the concentration of the salts and urea, and shows the resulting breaking strengths and colors produced.

TABLE 11 1 Effect of Urea on Fabric Breaking Strength with Various Ratios of Chromic and Ferric Chlorides in Mineral These results show the buffering effect of urea on heat ten dering of fabrics on mineral dyeing with these chloride salts. When 10 percent urea was added to the treating solutions.

there was no loss in breaking strength at any ratio of the two chloride salts.

EXAM PLE 4 It is well-known that N-methylolmelamine resins confer appreciable rot resistance to cotton fabric. It was believed that such nitrogeneous compounds would also buffer the heat tendering effect of chromic chloride mineral dyeing on cotton fabric as well as result in some rot resistance. A commercial trimethylolmelamine was used to prepare a solution containing 17 percent resin solids with 5 percent chromic chloride which also served as the catalyst for the resin and 0.2 percent wetting agent. The lined 8 duck fabric samples were heated 2, 3, and 5 minutes at 282 F. They were washed and dried after the usual hot alkali treatment. These samples were tested for initial breaking strength and rot resistance in soil burial beds. The following table shows this data.

5 TABLE IV.EFFECT OF DRYING TIME AND TRIMETHYL- OLMELAMINE RESIN (TMM) ON BREAKING STRENGTH AND ROT RESISTANCE OF MINERAL DYED COTTON DUCK FABRIC Breaking strength, 1bs..

Resin added (all Drying Weight alter soil burial, wks. 10 solutions contained time, add-n,

% chromic chloride) min. percent Initial 1 2 4 6 The above results show that at 5 minutes of heating at 282 F. there was some buffering effect due to the presence of the nitrogeneous resin. The breaking strength was 103 lbs. with the resin and 88 lbs. without the presence of the resin. Of course, some of the loss in fabric strength is due to possible cross-linking of the resin and the cellulose. Yet the overall strength losses are not as great with the resin present as when fabric was treated with chromic chloride alone. A heating time of 3 to 5 minutes seems to be required for the resinification of the trimethylolmelamine to be effective for best rot resistance.

EXAMPLE 5 The addition of urea to the chromic chloride-trimethylolmelamine resin solution should reduce the amount of strength loss in treated fabric yet retaining an appreciable amount of rot resistance. In the following eiiperiment lined 8 oz. duck fabric was treated with a solution containing 5 chromic chloride and varying amounts of trimethylolmelamine and urea and 0.2 percent of a wetting agent. After padding, the fabrics were dried in a gas oven for 5 minutes at 282 F., then padded with hot caustic-soda ash solution, finally washed and dried. The fabrics were tested for initial breaking strength and for rot resistance in soil burial beds. The results from this experiment are shown in the following table.

Breaking strength, lbs.,

Resin added (all Added Weight after soil burial, wks.

solutions contained urea, add-on. 5% chromic chloride) percent percent Initial 1 2 4 6 None 7. 9 86 None 9. 4 89 None 11. 9 79 The above experiment shows that an increase in urea content in chromic chloride-trimethylolomelamine treating solutions results in fabric with higher initial breaking strengths, again indicating the excellent buffering effect of urea. The best rot resistance as shown by fabric treated with solutions containing the resin without the urea. in these samples, the initial breaking strengths were lower. Adding urea to the resin formulations reduced the rot resistance of the treated fabrics somewhat but it was still at sufficiently high-level for applications not requiring exposure or direct contact with soil. A treatment with chromic chloride mineral dyeing formulations containing 10 percent trimthylolmelamine resin and 10 percent urea would be adequate for weather resistance.

EXAMPLE 6 The chromic chloride treating solution was modified by the addition of N-methylolurea resin both with the without added urea. A commercial urea formaldehyde resin was used in 6 percent and percent concentration in the 5 percent chromic chloride solution. Urea where used was at 10 percent concentration. Lined 8 oz. duck fabric was padded with the solution, dried in the gas fired oven for 5 minutes at 282 F., treated with hot caustic-soda ash solution, then washed and dried. The following table shows the results of initial breaking strengths and rot resistance.

TABLE VI.-EFFECT OF UREA FORMALDEHYDE RESIN (UF) AND UREA ON BREAKING STRENGTH AND ROT RESISTANCE OF MINERAL DYED COTTON DUCK FABRIC Breaking strength, lbs.,

Rosin added (all Added Weight after soil burial, wks. solutions contained urea, add-on. 5% chromic chloride) percent percent Initial 1 2 4 6 None 7. 9 86 85 14 10 7. 4 119 98 6 None 10. 2 81 76 90 69 66 11. 9 123 109 39 3 2 None 11.2 72 68 84 77 76 10 15. 7 107 104 85 32 22 134 16 Fabric treated with urea formaldehyde resin without the added urea resulted in lower breaking strength but good rot resistance. Adding urea improved the breaking strength con sidcrably but with somewhat reduced rot resistance.

We claim:

1. A mineral dyeing process for imparting to cellulosic tex' tiles improved dimensional stability, resistance to actinic degradation, and resistance to microbial degradation while tendering of the textiles associated with the use of metal 6 chlorides upon overdrying is minimized, comprising:

a. impregnating a cellulosic textile with a solution containing: about 5 percent of an inorganic salt selected from the group consisting of: chromic chloride, and ferric chloride;

about from 6 percent to 20 percent of an N-methylol resin to minimize fabric degradation and to impart rot and weather resistance, said resin being selected from the group consisting of trimethylolmelamine, and ureaformaldehyde;

about from 5 percent to 10 percent urea to bufier the tendering effect of the chloride; and

about 0.2 percent of a wetting agent;

b. removing the excess solution from the impregnated cellulosic textile to obtain a wet pickup of about from 40 percent to 70 percent,

c. drying the the wet impregnated cellulosic textile for about from 3 to 5 minutes at a temperature of about 282 F to insure drying and polymerization of the N-methylol resin,

d. impregnating the cellulosic textile from c. with a hot (about F.) solution containing about 1.6 percent sodium hydroxide and 2.8 percent sodium carbonate, and

e. washing the resulting textile free of alkali and drying it.

2. The process of claim 1 wherein the selected inorganic salt is chromic chloride.

3. The process of claim 1 wherein the selected is ferric chloride.

4. The process of claim 1 wherein the inorganic salt is a mixture of chromic chloride and ferric chloride.

5. The process of claim 1 wherein the N-methylol resin is trimethylolmelamine.

6. The process of claim 1 wherein the N-methylol resin is ureaformaldehyde.

inorganic salt 

2. The process of claim 1 wherein the selected inorganic salt is chromic chloride.
 3. The process of claim 1 wherein the selected inorganic salt is ferric chloride.
 4. The process of claim 1 wherein the inorganic salt is a mixture of chromic chloride and ferric chloride.
 5. The process of claim 1 wherein the N-methylol resin is trimethylolmelamine.
 6. The process of claim 1 wherein the N-methylol resin is ureaformaldehyde. 